Investigating Factors Impacting Carbon Dioxide Adsorption to Shale Rock and Their Effect on Carbon Dioxide Storage Capacity

During Carbon dioxide (CO₂) injection in shale reservoirs, a portion of the CO₂ may adsorb to the rock surface, and can thus be stored in the shale reservoirs. Many factors will impact the ability of the CO₂ to adsorb to the shale rock, and the capacity of CO₂ adsorption. This research investigates the factors that can impact the CO₂ storage capacity through adsorption in shale reservoirs and the impact of each factor. The factors that impact CO₂ adsorption can be divided into three main categories, including reservoir conditions, operational factors, and rock properties. The reservoir conditions include the reservoir pressure and temperature, and fluids within the pores of the reservoir. Generally, high pressures are considered favorable for CO₂ storage since the CO₂ will be compressed and thus a larger volume will occupy the available adsorption sites. High temperatures on the other hand are not favorable due to the increase in the activity of the CO₂ molecules and thus a lower tendency for adsorption. Operational conditions includes the CO₂ injection pressure, CO₂ purity, and CO₂ state, including gas, liquid, or supercritical. A lower concentration of impurities associated with the CO₂ will increase its adsorption capacity, since CO₂ exhibits physisorption, which is a multi-layer adsorption, and thus any impurities can result in a lower adsorption capacity. The rock properties are extremely important, especially the mineralogy of the rock, and the clay content. Any minerals within the shale that is soluble with CO₂ can pose some problems for long-term CO₂ storage. Also, a high percentage of clays will increases the CO₂ storage capacity, since the clay structure in the shale network allows for a higher availability of adsorption sites. This research investigates some of the main factors that can impact long-term CO₂ storage in shale reservoirs and their impacts on CO₂ storage capacity.